Connecting the Chemical Composition of Fine Particulate Matter (PM2.5) with Its Oxidative Potential: The Role of Redox-active Components

Presenter: Dr. Haoran Yu, University of Alberta

About the presentation: Fine particulate matter (PM2.5) significantly impacts health, and the expression of oxidative stress has been proposed and demonstrated as a significant biological pathway of the health effects of PM2.5. Oxidative potential (OP) serves as an important indicator for representing the expression of oxidative stress and in assessing the health implications of PM2.5 exposure, which has been demonstrated to be associated more directly with health outcomes than mass concentration alone.

Our investigation focuses on the patterns and roles of the redox-active components of PM2.5 in determining OP. In our first study, we employed a dithiothreitol (DTT) assay to study the interactions among PM components, including organic species (e.g., quinones and ambient humic-like substances, HULIS) and transition metals (e.g., Fe, Mn, and Cu) known to exhibit substantial OP. This approach highlighted the presence of ubiquitous interactions and revealed that the intensity of these interactions varies between DTT depletion and hydroxyl radical generation. Next, we explored the molecular characterization and OP of HULIS in PM2.5 through sequential extraction and analysis of three ambient PM2.5 samples. The extraction process aimed to separate components based on hydrophilicity and polarity, with analysis revealing a correlation between the chemical composition of more polar extracts and DTT activity. This indicates the significant role of polar redox-active chemicals in determining OP.

Finally, we investigated the chemical composition of PM2.5 collected from five distinct locations at urban, roadside and rural environments in Midwestern region of the United States, and associated them with five acellular oxidative potential (OP) endpoints of water-soluble PM2.5. We observed significant correlations of redox-active metals (i.e., Cu, Fe, and Mn) and carbonaceous species across most OP endpoints, further supporting their dominant contribution to OP. Our source apportionment analysis using the Positive Matrix Factorization (PMF) model across different environments in the Midwestern US also emphasized the discrepancy between sources contributing to PM2.5 mass and those affecting its OP. While regional secondary sources and combustion-related aerosols were major contributors to PM2.5 mass, local sources with marginal contribution to mass played a more significant role in influencing various OP endpoints.

This comprehensive study underscores the complex nature of health effects of PM2.5 linked to its chemical composition rather than bulk mass, highlighting the importance of considering more health-relevant indicators in air quality management strategies. Future work will delve deeper into the roles of specific organic species and leverage machine learning to predict OP of PM2.5 based on its chemical composition and source contributions, thereby enhancing our understanding of the health implications of ambient pollutants.

Presenter Bio: Dr. Haoran Yu is an Assistant Professor in the Department of Civil and Environmental Engineering at the University of Alberta, where he has been a faculty member since January 2024. He earned his undergraduate degree in Applied Chemistry from South China University of Technology in 2013. Pursuing further education in the United States, he obtained his M.S. in Environmental Engineering and Sciences from the University of Florida in 2016, followed by a Ph.D. in Environmental Engineering from the University of Illinois Urbana-Champaign in 2022, where he worked under the guidance of Vishal Verma. After completing his Ph.D., he joined the University of California Davis as a postdoctoral researcher until July 2023, collaborating with Dr. Anthony Wexler.

Dr. Yu’s research interest lies in understanding the health effects of atmospheric pollutants. His work aims to improve public awareness of the hazardous effects of ambient particulate matter (PM) by developing and investigating a more robust and simple health-relevant metric of PM. Currently, he leads projects on the development of a system for automated oxidative potential (OP) measurement, investigating the various roles of ambient particulate organic species in OP, and developing a machine learning model to elucidate the connections between the composition and sources of PM2.5 and their OP expressions.

Cost: $40 – A&WMA Members / $50 – Non-Members / $15 –Students (includes hot lunch & coffee). All prices include GST.CPANS is also pleased to offer this luncheon as an Online Webinar option. Individual webinar cost is $20.

Venue: University Club of the University of Alberta

11435Saskatchewan Drive

Edmonton, Alberta, T6G 2G9

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